Rear shocks /swingarm

[diyduneman]

This first time building go kart / dune buggy. I can't figure out why my rear swing arm isn't working , when I remove jack the whole kart pivots like if there is no shocks there to support it and saggs . Any idea what am doing wrong ?

 

[ezcome-ezgo]

Pancho spoke to this in the other thread. This is a leverage problem.

 

[diyduneman]

Pancho spoke to this in the other thread. This is a leverage problem.
View attachment 136137

Thanks for the diagram, who's Pancho? Can you provide more details about this diagram? , should I try diagram b?

 

[Snaker]

Pancho spoke to this in the other thread. This is a leverage problem.
View attachment 136137

Fantastic diagram.
Another factor also plays in, the spring.


Dia A would allow much more travel at the wheel then dia B, assuming the same spring (coil over shock) on each.
The ratio of shock travel to wheel travel

-AND/OR-

Dia A would need a much stronger spring then dia B to support the same load.

 

[diyduneman]

Fantastic diagram.
Another factor also plays in, the spring.


Dia A would allow much more travel at the wheel then dia B, assuming the same spring (coil over shock) on each.
The ratio of shock travel to wheel travel

-AND/OR-

Dia A would need a much stronger spring then dia B to support the same load.

Thank you for your reply , I really appreciate it, I should have payed attention Engineering class in high school . So which one do you recommend me building diagram A or B ? If A how do I know the size and weight capacity of the struts or shocks I need?. Also do they need to be exactly behind the 2 bars standing or can it be like the picture I provided with middle bar supporting the shocks?.

 

[diyduneman]

Close up pix of shocks , I think these shocks are no good plus the mounts are too big.

 

[Snaker]

Hard to say.
Its either some complex calculations or a lot of fabrication, pass or fail.

The tubing looks pretty thin?
The longer the swingarm is beyond the lower shock mount, the more stress that it will see.

So the closer that mount is to the wheel, the lighter the swingarm can be.

But again, the farther from the swingarm pivot, the less wheel travel you will have.
And the longer the swingarm is before the lower shock mount, the more stress that it will see.

 

[diyduneman]

Hard to say.
Its either some complex calculations or a lot of fabrication, pass or fail.

The tubing looks pretty thin?
The longer the swingarm is beyond the lower shock mount, the more stress that it will see.

So the closer that mount is to the wheel, the lighter the swingarm can be.

But again, the farther from the swingarm pivot, the less wheel travel you will have.
And the longer the swingarm is before the lower shock mount, the more stress that it will see.

The tubing is 1.5 inch solid steel . The kart is heavy I'd say 200 lbs

 

[Functional Artist]

Howdy,

Them looks like some automotive type, coil-over shocks
I had the same idea
...& "ran" into this same type of an issue, while building a kart (~20 years ago)

I agree, moving the lower shock mounts closer to the axle will help
but,
I think that you may need to pre-load them shocks a bit too
but then,
You'll probably need to add some "stops"
...so, the frame doesn't "arch" when you (unload it) get off or out of it

* I pre-loaded the shocks, on the kart I was building, by continually adjusting the upper shock mount downwards
...& "testing" (just setting in it, until the frame stayed nice-n-straight & level)

 

[diyduneman]

Howdy,

Them looks like some automotive type, coil-over shocks
I had the same idea
...& "ran" into this same type of an issue, while building a kart (~20 years ago)

I agree, moving the lower shock mounts closer to the axle will help
but,
I think that you may need to pre-load them shocks a bit too
but then,
You'll probably need to add some "stops"
...so, the frame doesn't "arch" when you (unload it) get off or out of it

* I pre-loaded the shocks, on the kart I was building, by continually adjusting the upper shock mount downwards
...& "testing" (just setting in it, until the frame stayed nice-n-straight & level)

Yes I bought these shocks instead, I'll keep yall updated once I get them in couple of days. I appreciate all the responses and help.

 

[redflash]

wow...it looks like you're trying to bolt the whole thing together without welds......with the flex and vibration of moving over ground....those nuts and bolts will loosen and fall apart. So your shocks ultimately really are immaterial.
I appreciate your ingenuity attempting to assemble with bolts.....but you NEED a solid welded frame without holes in them.......I suggest you scavenge around for an old REAL go Kart frame for a few hundred dollars and assemble something that will hold together. Or buy an inexpensive welder and learn to weld. Don't mean to be depressing, but that frame is not safe for man or child.

Da redflash

 

[diyduneman]

wow...it looks like you're trying to bolt the whole thing together without welds......with the flex and vibration of moving over ground....those nuts and bolts will loosen and fall apart. So your shocks ultimately really are immaterial.
I appreciate your ingenuity attempting to assemble with bolts.....but you NEED a solid welded frame without holes in them.......I suggest you scavenge around for an old REAL go Kart frame for a few hundred dollars and assemble something that will hold together. Or buy an inexpensive welder and learn to weld. Don't mean to be depressing, but that frame is not safe for man or child.

Da redflash

Thanks for your input , all bolts are stainless steel with locking lug nuts. So impossible for the them to get loose

 

[redflash]

you have never ridden a go kart then///////pay attention ...you asked for knowledge from experienced men. I know that may be depressing after all the work you've done........but listen up ,,, and learn !

Denny, panch...am I way off base ? help this guy

Da redflash

 

[diyduneman]

Thanks for your input , all bolts are stainless steel with locking lug nuts. So impossible for the them to get loose

Plus I figured I can get someone to weld it for me if I need to afterwords .

 

[diyduneman]

you have never ridden a go kart then///////pay attention ...you asked for knowledge from experienced men. I know that may be depressing after all the work you've done........but listen up ,,, and learn !

Da redflash

Why you mad though?

 

[diyduneman]

I watched couple of videos prior to building my cart , example this one shows you how to build without welding

Plus like I said , I can have someone weld it for me as am not a professional welder.

 

[redflash]

I'm not mad, just trying to keep you from hurting yourself...Can't weld that stuff, it's galvanized. the holes will make it weaker,,,and just because some one makes a pretty video doesn.t mean he didn't kill his child two weeks later, we here are obsessed with doing things the right way, and the safe way.......we have too many scars to suggest otherwise.

Da redflash

 

[ezcome-ezgo]

Sorry I fell short in my descriptions. I feel that diagram A is what you have, diagram B will give you better results without having to get different shocks.

 

[diyduneman]

I'm not mad, just trying to keep you from hurting yourself...Can't weld that stuff, it's galvanized. the holes will make it weaker,,,and just because some one makes a pretty video doesn.t mean he didn't kill his child two weeks later, we here are obsessed with doing things the right way, and the safe way.......we have too many scars to suggest otherwise.

Da redflash

Thank you for your input definitely wouldn't want to hurt my self driving it or others , so what makes you think it will break? Screws hold thousands of pounds . The frame it self isn't galvanized its solid steel , only galvanized is rear arm seing and front suspension of which I can have someone replace it and get it welded , this project was started for just fun and am not made even if made mistake , willing to correct some things that I why I registered on here so I can hear everyone's inputs and I appreciate raising concerns about it and would love to hear more of your ideas in going forward with what you think should be added or changed , but definitely not the whole thing is galvanized.

 

[diyduneman]

Sorry I fell short in my descriptions. I feel that diagram A is what you have, diagram B will give you better results without having to get different shocks.

Great thank you , I'll keep you updated with the project.